Check out this chapter from this book about race and IQ. It explains how human beings originally came out of Africa, and how geography and climate affected the intelligence of people in each region of the world.

Any book that mentions that garbage theory of "Out of Africa" goes straight to my waste basket.

I do not think everybody evolved directly out from Africa.

I also do not believe that Neanderthals went completely extinct.

Scientists like to be politically correct and state that neanderthals and homo erectus did not interbred with homo sapiens from Africa.

That is totally wrong. there was a study, I cannot find the link, that stated that every racial group, with the exception of a lot of black/Africans, has some trace of Neanderthal DNA in them.

There is a little more Neanderthal DNA in East Asians compared to Caucasian people. I think we evolved separately in various regions of the world, but somehow, these bi-peds from different species met somewhere and interbred with each other which probably formed the different racial groups we have on this planet.

There has to be a major link of all humanoid species for reproduction to take place and that is why I believe we all originally came from Africa and they have traced all our DNA back there as well as found many more variances in African DNA from different tribes compared to the rest of all the other races which means they have been here much longer than the rest of us.